If you're like me, you love ironing as much as the lady in this picture. Hauling out the board and finding space to set up and a place to set the iron without fear of melting something nearby are all a big pain. I have found a cheat that will help you come pretty close to an ironed look that is infinitely easier and less time and space consuming.
It is ideal to do this the night before you need to wear something, but if that's not an option you'll want to give yourself as much lead time as possible. (I want to add a disclaimer here: this technique is not advisable for garments you will wear to really important events like weddings, funerals, and job interviews. Those occasions deserve proper ironing respect.) Do not use this technique on a garment that will be shrunk, spotted, or otherwise ruined by water. If in doubt, put a small bit of water in an inconspicuous place (like inside the hem or at the bottom of the placket) and let dry thoroughly to see the result.
First, hang your garment. If it is a shirt, hang it carefully and button the front. Make sure it is hanging symmetrically. If it is knit, make sure your hanger won't cause "hanger bumps" on the shoulders or arms. If it is a skirt, hang it from a clip hanger by the waist. If it is a pair of trousers, hang them with a clip hanger upside down by the hems, inseams together (like you're making a sandwich... outseam, inseam, inseam, outseam), the clips gripping the center backs and center fronts of the legs.
Second, grab a clean spray bottle that has a mist setting and fill it with clean water. This would be a bad time to spray oily or chemically stuff onto your clothes, so I don't recommend reusing an old cleaning spray bottle.
Now begin spritzing your garment. I usually put my hand inside the garment to add some tension which helps to smooth the wrinkles and spray from the top down. You'll end up getting the garment damp, but it shouldn't be anywhere near dripping. Put a towel down to catch the mist that will fall to the floor.
Last, smooth or pull out any stubborn wrinkles, using more water if necessary and allow the garment to air dry undisturbed.
It's not as crisp as ironing, but considering that you're going to get wrinkled in the car anyway, it's a good second choice!